The present invention is directed to control valve means for a dental service.
Tappet valves or diaphragm valves have been utilized in medical, particularly dental devices, for the control of the flow of agents such as air, water and mixtures thereof. When a diaphragm valve is utilized, a diaphragm is clamped between two valve body parts and the diaphragm is then charged on one side with a control agent, for example, air, so that it closes two openings on the other side of the diaphragm. One of these openings extends to an agent feed line and the other to a discharge line. Thus, with the diaphragm closing these openings, flow between the input or feed line to the discharge line is prevented and when the control agent is released, the diaphragm will move to uncover the two openings to allow flow between the input and discharge lines. Examples of such control valves are disclosed in U.S. Pat. No. 3,918,161 and U.S. Pat. No. 4,136,450 whose disclosures are incorporated by reference thereto.
Diaphragm valves of the above-mentioned type are relatively susceptible to sticking as well as to deposits on or in the valve seat area so that the required tightness at the closed valve can very quickly disappear under given conditions. Thus, the operational reliability of the control valve means will deteriorate. This is also true of the former tappet valves or, respectively, of a combined diaphragm and tappet valves, particularly given their use for controlling aqueous agents because the particular dangers exist that the parts of the valves such as the tappet, compression springs, etc. will lead to a premature failure of the control valve means because of corrosion of these parts.